Deep inside the condemned building, a person hides in a closet, the door closed tight. Outside the room, far down a long hallway, a black Labrador Retriever is released. The dog bolts down the corridor, darting in and out of empty rooms as if pulled by an invisible leash.

When the dog reaches the last room at the end of the hall and smells its quarry, it barks and scratches at the door until the person emerges, rewarding the animal with praise and a rough tug of war with a toy.

The debris-littered building is a close approximation of a structure that's been pounded by a hurricane or other disaster and helps prepare canine search-and-rescue teams for finding an injured survivor lying buried beneath piles of rubble.

Outside, another dog, Kaiser, watches intently as other teams of dogs and their handlers file into the dilapidated structure for their turns.

Though his spirit is clearly willing, Kaiser is nearly 13, and his body can no longer meet the rigorous demands of SAR work. So the German Shepherd Dog watches the exercise while owner Tony Zintsmaster offers the occasional reassuring word or ruffles the dog's ears.

Courtesy of Bob Kaufman/Alaska.org

Kaiser and Zintsmaster are veterans of numerous disasters, both natural and man-made. Zintsmaster has worked for more than 20 years in canine search and rescue. His most memorable deployment, however, was the nine days he and Kaiser spent as part of Indiana Task Force 1 at what remained of the World Trade Center after the attacks on Sept. 11, 2001. "The scene was surreal," he recalled, adding how he could smell the site from blocks away.

"The gray dust was ankle-deep, black smoke, white smoke, fires burning, three cranes, two dozers, five claws, and 500 workers, working on our corner of an 80-foot-tall rubble pile, illuminated by high-powered lights from a dozen generators," Zintsmaster said.

On day two, Kaiser, preceding Zintsmaster up a part of the pile, stopped short and refused to move. "I reached down and discovered that the ground was hot," he explained. Fires were still burning beneath the rubble, and the ground could have easily collapsed beneath a worker.

That was a decade ago, and the years have caught up with Kaiser. Zintsmaster retired his dog from SAR work in 2010 after he saw Kaiser struggle up a debris pile. He's now training Kaiser's successor, Jago, a 4-year-old German Shepherd Dog, for certification by the Federal Emergency Management Agency as an SAR dog.

Of the hundreds of dogs that participated during the 9/11 disaster, few are alive today. The median age of the dogs at that time was 5 years, and soon they all will be gone. As the country marks the 10th anniversary of 9/11, Kaiser, like all the SAR dogs the nation took some small comfort in during those dark days, is a reminder of the remarkable ability these creatures possess to serve man, both body and soul.

Lynne Engelbert and Lucy, part of California Task Force 4, working at what was left of the Marriott Hotel near the World Trade Center

Courtesy of Lynne Engelbert and Tom Clark

In the immediate aftermath of the attacks, images of the SAR dogs guided by their handlers across the ruined backdrop were snapshots of hope amid so much carnage. And for so many of those who joined in the rescue and recovery efforts at the World Trade Center, the Pentagon, and the field near Shanksville, Pa., where United Flight 93 crashed, the chance to pet one of the dogs was a welcome break from the grim work.

Prior to 9/11, the public knew little about SAR dogs and what they are capable of, according to Dr. Cindy M. Otto, director of the Penn Vet Working Dog Center at the University of Pennsylvania School of Veterinary Medicine. But that changed once the news media seized on the dogs as one of the few positive narratives they could tell.

"When people saw or touched the dogs, they would relax or have a moment's hope. It was incredible to see the power those dogs had," noted Dr. Otto, who deployed to the WTC as a member of the Pennsylvania Federal Urban SAR team to assess and treat the dogs as they returned from the rubble.

Search and rescue is one component of canine detection, which ranges from locating explosives, firearms, and narcotics to tracking people and animals. Law enforcement, military, and government agencies capitalize on the dogs' abilities to support these missions. More than a dozen breeds have been used for detection work, but German Shepherd Dogs, Labrador Retrievers, and Belgian Malinois dominate the field.

"I lost Lucy when she was 15 1/2. Because she was so afraid of the vet's office, I carried her to her favorite place—the rubble pile—and we let her go there. I choose to believe that her spirit is still roaming the rubble, looking for lost souls."

—Lynne Engelbert, deployed with Lucy as part of California Task Force 4 to the World Trade Center

Dr. Robert L. Gillette is director of the largest dedicated academic research program for canine detection in the United States: the Canine Detection Research Institute at Auburn University's College of Veterinary Medicine. He remembers how, during the '80s, much work went into creating a machine capable of mimicking a dog's powers of detection. Eventually, the project was scrapped as a fool's errand.

"A lot of research went into that, but what we found out is you can't replace the dog. They're efficient, they're mobile, and they're driven to do these things," Dr. Gillette said. Because the limits of the dog's detection abilities are constantly expanding—just recently. dogs were used to find pythons released into the Florida Everglades—Dr. Gillette believes dogs will be effective in search-and-rescue scenarios that haven't yet occurred to us.

Denise Corliss of Texas Task Force 1 and Bretagne at the World Trade Center

Courtesy of Texas Task Force 1

Canine SAR teams have been receiving less public attention in recent years, even though there's been no corresponding drop in demand for their services. Linda Blick wants to reverse that trend. She co-chairs the Finding One Another project, a 9/11 anniversary tribute started by the Tails of Hope Foundation to honor the 10-year anniversary of the canine search-and-rescue teams that served at that time. AVMA Veterinary Medical Assistance Teams are participating in the memorial ceremony at Liberty State Park in Jersey City, N.J., intended to recognize the SAR teams and remind the public about their value.

"These are unique skills the dogs use for the betterment of our society," Blick observed.

Finding One Another is creating a historical registry with the names of the dog teams that served during 9/11. So far, more than 950 teams have been added to the list. Once the registry is complete, the project will present it to the National September 11 Memorial and Museum at ground zero.

For Blick, the dogs and their handlers are "unsung heroes," and she worries their contributions and sacrifices then and now aren't fully appreciated, especially because the handlers give so much, often putting themselves and their pets at risk.

Penny Sullivan has been part of detection dog work since the '60s. Sullivan has gone through numerous deployments, including to the World Trade Center with Quest, her German Shepherd Dog, who has since died, and has written extensively about the field. She was a member of the FEMA subcommittee to develop search-and-rescue dog criteria for disaster response. Sullivan estimates a handler spends approximately $2,000 annually on SAR dog-related expenses, including training and certification, not counting veterinary expenses.

"Most SAR teams are entirely volunteer," Sullivan explained. "They give freely of their time and service so that others may live. We are definitely in need of programs to benefit our working dogs and handlers—programs such as those to fund medical research to address the many health issues affecting our dogs over time."

Blick anticipates Finding One Another will be a mechanism of ongoing support for the canine SAR community. Plans include underwriting veterinary expenses, public education campaigns about the teams' work and needs, and even a White House conference on the subject.

Sadly, few 9/11 dogs will be present for the anniversary tribute in New York. For the past several years, Dr. Otto has monitored nearly a hundred 9/11 dogs. Of the original study group of 95 dogs, just 13 remain. Dr. Otto is part of a team of researchers trying to determine whether exposure to environmental contaminants at the World Trade Center and the Pentagon caused the dogs any ill health effects.

Unlike many of the human 9/11 responders who have reported a range of mostly respiratory-related illnesses, the search-and-rescue dogs fared remarkably well. "We really are hard-pressed to identify any consistent finding that can be associated with 9/11," Dr. Otto said.

"We train differently now. We know that we have to expose the dogs to masks and respirators. Dogs key in so much on body language, facial expressions, emotions, that you need to train with all the gear so the dogs think it's no big deal."

—Kim Lark, deployed with Sage as part of New Mexico Task Force 1 to the Pentagon

One possibility is that the long canine nose filters out the airborne contaminants more effectively than the shorter human nose. Another theory is the canine immune and respiratory systems are better at preventing reactive respiratory diseases. Researchers are now looking at whether the 9/11 dogs have a higher incidence of hemangiosarcoma or lymphosarcoma, the most common cancers in many breeds of dogs that worked at the World Trade Center and Pentagon.

Other studies are under way to identify various components that make the ideal detection dog. The American Kennel Club Companion Animal Recovery Group is funding one such study at the Penn Vet Working Dog Center, which houses a databank of DNA samples from approximately 273 detection dogs.

"We want to look at all of the things we're doing and figure out how do we make it better, how do we make it reproducible, and how do we improve the performance, health, and well-being of these dogs," said Dr. Otto, who is leading an AVMA VMAT initiative to train handlers in basic medical care for their dogs.

Also working to advance the field of canine search and rescue is the Scientific Working Group on Dog and Orthogonal Detector Guidelines. A partnership among government, private companies, law enforcement, and first responders, SWGDOG develops consensus-based best practices for detection dog teams. Dr. Gillette of Auburn University says standardization is essential, given the teams' work.

"There's got to be some way of making sure that the dogs are able to do what their handlers say they can do," Dr. Gillette explained. "You have training standards and management standards to make sure that the detection dog is a sound detection tool."